Having a larger diameter piston does provide more room that can benefit the flow. Also boost is a measurement of restriction so higher flow can move more air @ less restriction (ie boost).
~Induetime~ "Lag Less" First Stock Turbo to break 500WHP on boost alone. New track car project "Diseaze": http://arizonazproject.wordpress DOT com Custom fabrication for the Z32: search QFAB on Facebook More custom fabrication: search FuturFabrication on Facebook